This invention relates generally to radio transceivers, and, more particularly to a radio transceiver which is capable of automatically establishing the least congested channel for communication between parties making initial contact on a congested calling channel.
Radio transceivers combine the best qualities of radio transmitting and receiving equipment in a common housing, and as a result thereof, although not limited thereto, usually are portable and capable of mobile use. Subsequently, the applications of radio transceivers have become widely diversified. For example, transceivers are readily acceptable in areas of public safety such as marine and aviation communications, police and fire protection, forestry conservation and highway traffic control. In addition, transceivers are found in areas of industrial use, land transportation, the wide field of broadcasting, weather reporting and military applications.
Radio transceivers are typically built to operate on one or more discrete preset switch-selected radio frequencies (channels) rather than being continuously tunable over a band of frequencies. Heretofore, transceivers needed one or sometimes two quartz crystals per channel as frequency standards in their oscillator circuits. The cost and size penalty of this requirement limited the number of channels a transceiver could feasibly be built to handle. The recent development of digital frequency synthesizers in the form of monolithic integrated circuits does away with this limitation. A synthesizer performs a binary arithmetic operation on the output of a single crystal frequency standard, allowing the transceiver to tune a large number of channels. The operator merely sets the Channel Selector Switches to the desired channel.
A common procedure used with tactical radio transceivers, particularly where radio traffic is heavy, is to designate a calling channel or channels. Once contact is made on a calling channel, the parties agree to switch to an alternate channel. Unfortunately, with today's equipment, they have no way of knowing whether the alternate channel they are selecting is vacant, or whether it may at that moment be even more congested than the calling channel, causing possibly serious confusion and delay. Presently there is no equipment available which will allow, in a reliable and inexpensive manner, the utilization of radio transceivers so as to provide an optimal choice of alternate radio channels for parties making contact on a congested calling channel.